The invention relates to a blade holder for cutting machines, with a blade head held on a raising and lowering device, and with an adjustment mechanism for a circular blade that is held on the blade head, whereby for the movement of the circular blade between a cutting position and a ready position, the adjustment mechanism is provided with an adjustment piston rod having a compressed air activated adjustment piston that is guided in a chamber of the blade head housing, and the adjustment piston rod is biased via a compression spring into the ready position of the circular blade.
A blade holder having the aforementioned features is described in DE 4114 059 A1; the blade head that caries the circular blade is seated at the end of a lowering piston rod via which the circular blade can be lowered into its cutting plane and raised therefrom. The adjustment mechanism disposed in the blade head serves for an adjustment of the circular blade transverse to the axis of the lowering piston rod until it rests against a lower blade, or raises the circular blade from the lower blade beyond the cutting process.
To carry out these movement processes, the adjustment mechanism has an adjustment piston that is compressed air actuatable in a direction of the cutting position of the circular blade, while for the return movement of the circular blade out of the cutting position, there is provided a compression spring that acts upon the adjustment piston rod and biases it into the ready position of the circular blade. Thus, in addition to the pressing force in a direction of the cutting position of the circular blade, which pressing force overcomes the biasing compression spring and is applied by the compressed air supply to the adjustment piston, there is also provided the cutting force that exists between the circular blade and an associated lower blade.
Since over the adjustment path of the adjustment mechanism, depending upon the position of the blade holder on the cutting machine, different cutting positions with the circular blade resting upon the lower blade can result, the known construction of a blade holder has the drawback that at respectively the same air driving pressure, in different cutting positions different cutting forces are also established, because a respective spring force of the biasing compression spring, which spring force varies in magnitude as a function of the spring characteristics or of spring tolerances, counteracts the air driving pressure in the various cutting positions.
It is therefore an object of the invention, with a blade holder of the aforementioned type and with an unaltered air driving pressure over the adjustment path, to establish for the adjustment mechanism a cutting force that remains as constant as possible in different cutting positions of the circular blade.